1. Technical Field
The present disclosure relates to semiconductor devices, and, more particularly, to a precharge method for a semiconductor memory device and a semiconductor memory device using the same.
2. Discussion of Related Art
Semiconductor memory devices, particularly dynamic random access memories (DRAMs), typically need a precharge operation to perform normal operations.
Due to a demand for increasing the integration density of semiconductor memory devices, the semiconductor memory devices have been made with a multiple bank structure. In response to a precharge command, a semiconductor memory device having a plurality of banks may perform not only a precharge operation of precharging each bank but also an all-bank precharge operation wherein all banks are precharged at once.
The precharge operation may involve applying a bank address BA for a bank to be precharged along with the precharge command to the semiconductor memory device. Also, the all-bank precharge operation may involve applying an all-bank precharge command even without applying the bank address BA.
The corresponding bank may receive an active command ACT and then be precharged after a row active time tRAS has elapsed. The row active time tRAS may be defined as the sum of the time taken for a sense amplifier to finish a sensing operation in response to a row address RA after the application of the active command ACT and the time taken to perform a data read or write operation.
The all-bank precharge command may be typically executed to initialize a semiconductor memory device before a mode register set (MRS) is changed or before the semiconductor memory device enters an auto-refresh or self-refresh mode. As described above, each bank may receive an active command and then be precharged after a row active time tRAS has elapsed, and the all-bank precharge command may allow all the banks to be precharged. Thus, a conventional semiconductor memory device may receive an all-bank precharge command, delay the all-bank precharge command for a predetermined time irrespective of a state of each bank, and perform an all-bank precharge operation.
However, since all banks of a semiconductor memory device may be precharged simultaneously during an all-bank precharge operation, a very large amount of power consumption may occur in an initial period of the precharge operation. The power consumption may add noise to the power supply voltage, thereby increasing the duration of the precharge operation or precluding a normal precharge operation. Also, even during a precharge operation of each bank, when a plurality of banks are precharged simultaneously, noise may occur in the power supply voltage. In addition, when each bank includes a large number of memory cells and all blocks of the bank are precharged simultaneously, noise may occur in the power supply voltage.